Despite the technical challenges, designers have an obligation to explore the potential to conserve and reuse heritage structures, says Richard Hill of Arup
While there is an inherent desire in our industry to build new and start afresh, it is pleasing to see a growing appreciation for heritage buildings and a desire to conserve them. Aside from the environmental benefits of extending the life of our existing structures, there are also many other invaluable social benefits.
Heritage buildings contribute to the sense of community that a place offers, with a significance that goes beyond the aesthetic – a building, or rather, a collection of buildings provide an insight into the past.
Therefore, regardless of whether a building is listed or not, engineers have a duty to see if an existing structure can be adapted with as much of the original fabric and character retained as possible. Sensitively repurposing heritage buildings plays a vital role in regeneration by providing a continued sense of place, resulting in stronger communities.
However, modern conservation is not about simply wrapping buildings up in cotton wool. Renovation and reuse go hand-in-hand. Adapting and repurposing buildings is an essential part of maintaining heritage. Even before we inherit them, many heritage constructions have seen many different prior uses throughout their lifespan, and often had significant alterations in the early stages of their use. Adaption and repurposing is therefore simply the next chapter in the building’s life. So how do we reuse successfully?
Respect in regeneration
Understanding the significance of a building’s heritage is vital to striking the right balance between conservation and adaptation. Conservation-accredited architects and engineers can offer essential insights as part of this process and both should be involved at the earliest possible stage. There is a delicate balance between ensuring new alterations are in keeping with the building’s scale and form, but that they can also be discerned from the original building so there is an honesty in the interventions.
This is more than simply replacing damaged materials and cleaning up facades – the latter of which can actually remove the patina that provides so much historic character. Engineers can be daring and go beyond relying on steel and glass.
As an example on Arup’s recent project renovating Coal Drops Yard in King’s Cross, one of our most striking alterations is the sculptural pitched slate roof that unites the two buildings. While using slates from the original quarry, it is clearly a contemporary addition to the original buildings.
This is not to say significant structural developments are not a massive undertaking requiring difficult decisions – not everything can be salvaged when it comes to adapting for modern audiences.
On the project in King’s Cross, a significant length of the East Coal Drop, for example, was ravaged by a fire in the 1980s, destroying the roof. This left the timber floors and iron beams to rot and corrode, and large structural cracks needed to be repaired in order to stabilise the perimeter walls. In addition, the introduction of lift and stair cores meant that a few of the original cast iron columns had to be removed. Fortunately, we were able to use these to replace cracked cast iron columns in other parts of the building, ensuring as much of the original fabric as possible could be preserved.
Balancing the scales
Viewing heritage work as something to be celebrated and enjoyed empowers engineers to ensure historic buildings are salvaged while allowing for modern functionality.
This was how Arup approached uniting the West and East Coal Drop buildings to create a successful future as a retail and foodie destination. One of the major challenges was the two buildings and their respective viaducts having four different floor levels. To unify the floor levels and provide step free access from the East Coal Drop to the West Coal Drop, the timber floor (including large timber beams) in the East Coal Drop was dismantled and lowered, while lightweight build up material was added to the viaducts to retain the original fabric. The large timber floor beams here needed to be stitched together with long screws enhancing their ability to carry load while being a very discrete and almost invisible intervention.
Also, the East Viaduct – a brick arched structure – was cut back at the north end to provide greater flexibility of space and pedestrian flow at yard level. This required careful temporary design work, with the new staircase designed to resist the outward forces of the retained arch.
How contemporary audiences will use heritage buildings is not the only concern for us. Renovating must also consider long-term future audiences. Throughout the Coal Drops Yard project, we were mindful to create different pockets of space to encourage seeing them from a new perspective with each visit and to ensure different focuses and uses could be met in years to come.
For example, the new roof and floating floor (which span the 33 m wide central courtyard), and glazed facade provide a unique and strikingly contemporary form that immediately captures people’s attention and draws them to the space. The mix of spaces and materials provide a unique character. This includes intimate spaces at the yard level from the cellular nature of the original building where coal was once distributed, to the larger more open spaces at the upper levels where the wagons travelled the length of the buildings.
The deliberate choice of materials was also a key decision as the raw mix of brickwork, timber and iron structural elements remain visible and are celebrated in the design. This avoids ageing the renovations, while maintaining that connection to the past and respecting the history of the buildings.
In the UK we are spoilt with a plethora of historic and heritage buildings to enjoy. But to give them a future use and protect them from disrepair and even destruction, renovating is of far more power and practicality than revering them.
Richard Hill is an associate director at Arup